1. Field of the Invention
This invention relates to coulometric electrolytic timing devices and more particularly to timing devices for designating an elapsed time period in response to current flow through an electrolytic solution.
2. Description of the Prior Art
U.S. Pat. No. 1,254,939 discloses a coulometric timing device having a cylindrical sleeve and a small hollow, cylindrical member coaxially aligned with the cylindrical sleeve which is filled and supported by a nonconductive material. A conductor is passed through the nonconductive material and a voltage applied to convert the cylindrical sleeve to a cathode and the hollow member to an anode whereby the anode plates away and onto the cathode. When the anode is completely plated away, heat is generated and causes the nonconductive material to melt and seal the conductive wire. When current flow stops, an alarm is activated.
U.S. Pat. No. 2,791,473 discloses a regenerable elapsed time indicator having an anode and cathode section with an electrolyte therebetween. When the metal is exhausted from the anode and metallic ions are depleted from the electrolyte, the voltage necessary for maintaining the current increases and activates the alarm unit.
U.S. Pat. No. 3,029,384 discloses an elapsed time indicator utilizing a dual coiled spring assembly with one spring coupled to a pointer. When an electrical circuit is established, metal from one spring is plated away and the pointer moves in response to the weakening of the spring to indicate an elapsed period of time.
U.S. Pat. No. 3,609,622 discloses a spirally-wound heater which is vaporized to deposit metallic ions onto a plurality of metallic bands. When sufficient metal has vaporized from the spiral heater and deposited between the metallic bands, the resistance between these bands are reduced. When a certain minimum resistance level is obtained the circuit is activated.
U.S. Pat. No. 3,355,731 discloses the use of a calibrated wire disposed within a cylindrical cathode perpendicular to the longitudinal axis. When the wire completely erodes away, the circuit is broken and the alarm circuit is activated.
U.S. Pat. No. 3,711,751 discloses an electrolytic timing device having a U-shaped anode portion within a cylindrical housing. The U-shaped anode allegedly achieved greater precision than other timing devices because of its ability to focus the removal of metal at a particular location, i.e., the arcuate portion of the U.